void main(List<String> args) {
  dynamic docker = 10;
  docker = "Docker";
  docker = true;
  docker = "docker Swam";
  docker = 23;
  docker = "docker";
  print(docker);
  docker = 123;
  docker = ["123456", 123, "张元英"];
  docker.forEach((element) {
    print(element);
  });
}
